This invention relates to an internal combustion engine ignition control system for producing ignition spark triggering signals which are proportional to preset advance control voltage signals. The ignition spark timing system proposed by this invention is specifically itended to widen the variable control range.
Conventional techniques have heretofore been primarily concerned with maximizing engine output and minimizing fuel consumption. In recent years, however, efforts have been made toward reducing the unburned resides in exhaust gases by prolonging the combustion of fuel in engine equipped with an auxiliary combustion chamber. A wide variable control range is necessary when attempting to regulate the ignition spark timing in engines of this type.
According to the technique for electrically controlling spark advance in spark ignition type engine various methods have been proposed for converting the advance control voltage signals to ignition triggering signals during specific crankshaft angles. In all of these conventional methods arithmetic operations are performed for a crankshaft angle in which the angle of rotation is within approximately 90.degree. for a four-cylinder engine; as a result, the control range is limited to only the remaining 90.degree.. A narrow control range means that control has a tendency toward instability in the vicinity of the control limits while accuracy deteriorates; these factors contribute to a pronounced narrowing of the practical range. Some of these conventional systems have also necessitated the utilization of signals other than the reference angle signals for the top dead center positions of the pistons and this has led to a need for complicated angle signal detecting devices which is an undesirable condition.